Subject: Spontaneous and induced creation of semi-classical objects. (Is it safe to run high-energy colliders?)

Semiclassical objects: solitons, bubbles, black holes, etc., can be viewed as field configurations consisting of very many quanta. In certain situations such objects can be formed spontaneously “out of nothing” or/and be produced in a thermal bath or in particle collisions. Some of them, if actually produced in a laboratory, may lead to catastrophic consequences. The impossibility of such a doomsday-type outcome of running high-energy accelerators has been fully tested “experimentally” by the cosmic ray collisions over the history of the Universe. I discuss possible theoretical explanations of this encouraging “experimental result”.

This colloquium will provide an introduction to the physics of spin transport in solids, with an emphasis on semiconductors. I will focus on the roles played by tunneling, spin-orbit coupling, and hyperfine interactions in the injection, transport and detection of spin-polarized electrons. Examples from experiments on ferromagnet-semiconductor junctions will be used to illustrate some of the unusual physics associated with these phenomena. The technological implications will be discussed briefly (and somewhat skeptically).

I present a nontechnical review of current understanding of the phenomenon of color confinement: from the conceptual roots of the idea related to Abrikosov vortices in superconductors to modern implementations of the dual Meissner effect in non-Abelian theories similar to quantum chromodynamics, the theory of hadrons. Supersymmetry was instrumental in recent developments. Efforts aimed at solving various aspects of QCD basing on supersymmetry and string-inspired ideas bring fruits. In a remarkable entanglement, theoretical constructions of the 1970s and 1990s combine with today's ideas to provide new insights.

We have constructed an instrument that records a complete time-domain laser fluorescence decay, resolved on the subnanosecond time scale, 10000 times per second, with high S/N and reproducibility. We are using this instrument to measure intramolecular and intermolecular distances in muscle proteins during their biochemical activities. This is accomplished by time-resolved fluorescence resonance energy transfer (TR-FRET), which can determine complex distance interprobe distributions in the range from 2 to 8 nm. When this experiment is performed following the rapid mixing of proteins and substrates, we record these signals resolved on the millisecond time scale of biochemical kinetics. This new experiment, called transient time-resolved FRET, (TR)2FRET, provides multidimensional structural information on the time scale of biochemical reactions. We have used it to define the internal structural dynamics of two muscle proteins during their ATP-driven energy transduction processes: myosin, which generates force in contraction, and the calcium pump, which relaxes muscle by removing calcium after a contraction. These studies are being used to determine how the molecular machine works, how it fails in disease, and how to repair it therapeutically.

The nature and identity of the dark matter of the Universe is one of the most challenging problems facing modern cosmology.
Supersymmetry offers a natural candidate for dark matter.
After a brief review of the evidence for dark matter, I will discuss the phenomenological consequences for supersymmetry both in the context of dark matter and upcoming experiments at the LHC.

In the BCS paradigm for the superconducting state, electrons close to the Fermi level EF-
form Cooper pairs which condense into a zero center of mass momentum state. This results in a gap in the electronic excitation spectrum that is symmetrically
centered about EF-
. Above Tc-
where the condensate is lost, the pairs dissociate, the energy gap collapses, and the normal state Fermi surface appears. On the other hand,in the underdoped high temperature superconductors, instead of a complete Fermi
surface above Tc-
, only disconnected regions of the Fermi surface appear, separated by regions that still exhibit an energy (pseudo)gap. After introducing the technique of angle resolved photoemission, used to study the electronic excitations in materials, we show that in this pseudogap phase, the energy-momentum relation of electronic excitations near EF-
behave as they do in a normal metal in regions with a Fermi surface, but like that of a superconductor in the gapped regions. We discuss these results in terms of competing order parameters, and the relationship between pairing and condensation

The year just finished witnessed the first beams of particles circulated in a new accelerator near Geneva, Switzerland -- the Large Hadron Collider (LHC). The event received remarkable media attention as well as intense scientific interest. This colloquium will discuss the physics goals of the collider, the experience of first beam, the subsequent failure of a portion of the machine, and the outlook for the near future both in the operation of the collider and the physics results to be expected.

Subject: Plans for the Facility for Rare Isotope Beams (FRIB) at Michigan State University

On December 11, 2008, the U.S. Department of Energy (DOE) announced “that Michigan State University (MSU) in East Lansing, MI has been selected to design and establish the Facility for Rare Isotope Beams (FRIB), a cutting-edge research facility to advance understanding of rare nuclear isotopes and the evolution of the cosmos.” In this talk I will provide a high-level summary of the envisioned science program, the facility layout and user interfaces for the planned facility. In addition, I will highlight existing and newly emerging rare isotope research opportunities for future FRIB users who can initiate or participate in cutting edge rare isotope research programs at the existing NSCL, which can seamlessly transition to FRIB.

Subject: What powers the intra-cluster filaments in large clusters of galaxies?

Refreshments served in Room 216 Physics after colloquium

The first radio surveys of the sky discovered that some large clusters of galaxies contained powerful sources of synchrotron emission. Optical images showed that the intra-cluster medium was permeated by long linear filaments with bizarre emission line spectra. Recent observations in the infrared and radio show that these filaments have very strong emission lines of molecular
hydrogen and carbon monoxide. The mass of molecular material is quite large, the gas is quite warm, and the filaments have not formed stars despite their multi-Gyr age. I will discuss the general astrophysical context of large clusters of galaxies and how large masses of molecular gas can be heated to produce what we observe.

The electron carry not only an electrical charge but also a spin. The spin can be viewed as a tiny magnet and, actually, the magnetism of matter is mainly related to the orientation of the spin of the electrons. Spintronics is a new type of electronics exploiting not only the charge of the electrons but also the influence of the spin on their mobility in magnetic materials. We are already familiar with spintronics since we use everyday the "Giant Magnetoresistance" (GMR) to read the hard disc of our computer or listen to music on our I-Pod. The discovery of the GMR, 21 years ago, kicked off the development of spintronics which is expanding today in many very promising directions. I will describe the most recent advances. The current researches will probably lead to a new type of memory (STT-RAM) for our computer, to smart radio-wave emitters for our telephone and, perhaps, to qubits for quantum computing.

Note different day for the colloquium, this week only. Refreshments served in Room 216 Physics after colloquium

The usual materials of classical spintronics are magnetic and nonmagnetic metals, magnetic and nonmagnetic semiconductors and, for tunnel junctions, insulating materials like MgO or alumina. However, nowadays, promising results begin to be obtained with a new family of materials which includes carbon nanotubes, graphene and several types of magnetic or non-magnetic molecules. The general advantage of carbon-based materials is mainly their long spin lifetime related to the small spin-orbit coupling of carbon, but, as we will see, the very high electron velocity of some of them is also of great interest for spintronics. The first part of the talk will be an introduction on classical spintronics and a review of what can be done with molecular materials for TMR, spin transport in lateral structures, magnetic switching or microwave generation by spin transfer. In the second part of the lecture I will focus on the general problem of spin transport in a nonmagnetic lateral channel between a spin-polarized source and a spin-polarized drain, a structure which is at the basis of several concepts of logic devices or spin transistors. The main difficulty is related to the transformation of the spin information – related to the magnetic configuration of the electrodes- into a large electrical signal, ideally Δ V/V ≈ 1 or larger, if V is the bias voltage and Δ V some voltage variation induced by a change of the magnetic configuration. In experiments on structures in which the lateral channel is a metal or a semiconductor, Δ V/V does not exceed a few 1% and the electrical signal Δ V is generally in the μ V range. In contrast, in the experiments on carbon nanotubes between ferromagnetic contacts we will present, high values of Δ V/V ( above 70%) and large Δ V (of the order of 100 mV) can be obtained. After a description of the theoretical background, we will discuss the origin of the difficulties for semiconductors and explain why large values of Δ V/V and Δ V can be easily obtained with carbon nanotubes. We will emphasize the potential of carbon nanotubes, graphene and other molecules for spintronics, and conclude by presenting some next challenges for molecular spintronics.

The human brain is a network containing a hundred billion neurons, each communicating with several thousand others. As the wiring for neuronal communication draws on limited space and energy resources, evolution had to optimize their use. This principle of minimizing wiring costs explains many features of brain architecture, including placement and shape of many neurons. However, the shape of some neurons and their synaptic properties remained unexplained. This led us to the principle of maximization of brain's ability to store information, which can be expressed as maximization of entropy. Combination of the two principles, analogous to the minimization of free energy in statistical physics, provides a systematic view of brain architecture, necessary to explain brain function.

Subject: Ending of the tyranny of copper: Intermetallic superconductivity in the post copper-oxide age.

In this colloquium I will present a broad overview of humanity's 100 year search for higher transition temperature, and generally more useful, superconductors. Particular emphasis will be placed on the past 20 years. The talk will start with an introduction to superconductivity (historically, phenomenological, and theoretically) and then progress through several of the key discoveries of the past one-score years. The basic conclusion is that this is a field that is still dominated by highly intuitive searches and sudden discoveries. That being said, the past decade has seen several discoveries that seem to point toward a very promising and rich phase space. The talk is intended to be a light and fluffy review of an exciting field. Mildly off color jokes about one and all will be included free of charge.

Graphene: the magic of electrons in flatland
Eva Y. Andrei
Rutgers University

Graphene, a one-atom thick layer of crystalline carbon possesses extraordinary electronic properties which make it a prime candidate for novel nano-electronic devices, at the same time raising the prospect to observe phenomena hitherto unseen in bench top experiments. These unusual properties are due to charge-carriers that behave like ultra-relativistic particles, also known as massless Dirac fermions. I will present scanning tunneling microscopy and transport experiments that provide access to these particles and give new insights their unique world.

Subject: Using the Aurora to Remote Sense Plasma Physical Processes in Near-Earth Space

Refreshments served in Room 216 Physics at 3:00 p.m. this week only.

Near-Earth space (or GeoSpace) is a plasma environment which sits between the Earth's atmosphere and the interplanetary medium. This region is populated by plasma that originates from the solar wind as well as our atmosphere, and is host to dynamic physical processes that are interesting not only in their own right, but also as examples of processes at work in the solar corona and more distant cosmic plasma systems. Large and small-scale electrodynamics are responsible for, among other processes, the Northern and Southern Lights, also known as the Aurora Borealis. While GeoSpace is close by, it is notoriously difficult to study. It is virtually impossible to image GeoSpace directly, and even fleets of satellites flown with state-of-the-art instrumentation provide point measurements within a vast region of space. The topology of the GeoSpace environment is largely controlled by the terrestrial magnetic field. The entire region is connected along magnetic field lines to the Earth's upper atmosphere, one consequence of that connection being the aforementioned Aurora Borealis. For more than fifty years, researchers have been struggling to develop the aurora as a means of remote sensing GeoSpace dynamics, providing a crucial compliment to direct satellite observations. In this talk, I will provide a brief overview of GeoSpace and some of the big questions that space physicists are addressing. I will focus on the aurora, and how we are now using state-of-the-art auroral observations to explore some specific questions such as how small-scale dynamics such as reconnection and MHD instabilities affect the global system topology in dramatic events called magnetic substorms.

The universe as understood through particle physics has an underlying structure
that interconnects mass, flavor and chirality in complex ways.
The neutrino is a fundamental fermion that is uniquely suited as a probe of this structure. I will review some of the properties of Standard Model of particle physics that we wish to better understand and will present the physics potential and status of the NOvA experiment, a detector under construction in northern Minnesota that is designed to observe the phenomenon of neutrino oscillation.

Cochlear implants are the first device to successfully restore neural function. They have instigated a popular but controversial revolution in the treatment of deafness, and they serve as a model for research in neuroscience and biomedical engineering. In this talk the physiology of natural hearing will be reviewed from the perspective of a physicist, and the function of cochlear implants will be described in the context of historical treatments, electrical engineering, psychophysics, clinical evaluation of efficacy and personal experience. The social implications of cochlear implantation and the future outlook for auditory prostheses will also be discussed.

About the speaker:
Ian Shipsey is a particle physicist, and a Professor of Physics at Purdue University. He has been profoundly deaf since 1989. Recently he heard the voice of his daughter for the first time, and his wife's voice for the first time in thirteen years thanks to a cochlear implant.

The laws of physics for matter and antimatter are very, very similar. Yet we live in a Universe where matter dominates over antimatter by many orders of magnitude. When and how did this imbalance occur? This is a question at the root of our existence, but one for which, as yet, we do not have a satisfactory answer. I will review the physics of this problem, and the possible answers that are suggested by our current understanding of the history of the Universe and of the differences between the behavior of matter and antimatter, known as CP violations.

Subject: A Microscopic Understanding of Exchange Anisotropy in Fe/MnF_2 Bilayers

Refreshments served in Room 216 Physics after colloquium

A microscopic understanding of the Ferromagnetic/Antiferromagnetic (F/AF) direct exchange coupling or exchange biasing has been elusive for the over 50 years since its discovery. In part, the almost exclusive use of hysteresis loops to study the phenomenon has limited our understanding. We developed a new experimental technique to study the exchange coupling between a ferromagnet and antiferromagnet [Appl. Phys. Lett. 69,3932-3931 (1996)]. This new technique enjoyed considerable success in explaining many general exchange bias features using Co/CoO as a model system [J. Appl. Phys. _87_, 6418-20 (2000), J. Appl. Phys. _89_, 7543-5, (2001), and Phys. Rev. _B 65_(RC) 180406-10(2002)]. After the Co/CoO work we used variations of the technique to study the angular dependence of the interfacial energy in Fe/MnF_2 bilayers. We were able to explain the observations using a microscopic model [Phys. Rev. _B 65_(RC), 100402, (2002), Phys. Rev. _B 68_, 054430 (2003)]. The microscopic model includes terms for the interfacial exchange coupling, uncompensated spin density in the AF, the AF spin-canting energy, and domain walls in the AF. Application of the model to the Fe/MnF_2 bilayer experimental data allows one to separately determine the fraction of uncompensated interfacial spins in the AF layer and the interfacial exchange coupling energy for the first time. An understanding of the spatial distribution of the microscopic energies allows for a simplification of the energy in which the physics is transparent.This work supported by the University of Minnesota MRSEC

Superconductivity is a powerful tool for the detection of electromagnetic radiation over an extraordinary range of frequencies. The superconducting transition-edge sensor (TES), for example, is an extremely sensitive detector over more than twelve orders of magnitude in frequency, from microwaves through gamma rays. The TES uses a superconducting film biased in the superconducting transition as a sensing element. TES arrays have evolved beyond the research and development phase, and they are providing improved sensitivity in applications as diverse as nuclear non-proliferation and forensics, nuclear and particle physics, and cosmology. These arrays are instrumented by superconducting quantum interference device (SQUID) amplifiers. I will discuss the development of these detectors, and highlight their use in nuclear non-proliferation and cosmology, where they are providing new capabilities for sensitive measurements of the elemental and isotopic composition of nuclear materials, and the power and polarization of the cosmic microwave background.

The discovery of CP Violation in kaon decays 1964 created quite a shock in the HEP community despite the fact that parity violation had been established a few years earlier. The impact of this discovery can be illustrated by the very peculiar theory that had been suggested for it: the KM ansatz seemed a priori unlikely to be correct. Yet since the turn of the Millenium it has been empirically validated in the decays of B mesons to an impressive degree -- while failing to provide a scenario for baryogenesis. This success of the Standard Model of HEP does not invalidate the experimental and theoretical arguments for its incompleteness. The task of uncovering the dynamics driving electroweak symmetry breaking provides our
generational challenge. It will be addressed by experiments undertaken at the LHC. A dedicated continuation of comprehensive studies of heavy flavour transitions will be a central element in confronting this challenge.

A few hundred thousand years after the Big Bang the primordial gas recombined, became transparent - the last light from that we now see as Cosmic Microwave Background. There was very little structure in the universe at that time, no source of light - we call it now the Cosmic Dark Ages. It would take several hundred million years before the first stars in the universe would form, making the first source of light after the big bang, when the "dark" matter could clump, collecting up baryonic matter that could cool down, and condense into the first stars. Still, the gas was quite warm, so it would take massive, big clouds to collapse under their own gravity, making big stars. At least, this is what out best theories tell us. But no one actually has ever observed this to date. So, is that story true? How big were the first star actually? What can we do to find out? Looking at the current universe, we do see that some quite big stars are still formed today, but they shed mass in massive winds and in giant eruptions and will die not quite as big as they were born. Is the same true for the first stars if born as big as the biggest stars we see today? Or were there even bigger stars, and how would the evolve and die? Could these latter once be the predecessors of the supermassive black holes harbored in the centers of even some of the earliest galaxies we see? So, how can we find out? At least part of the story we may be able to uncover now by looking at ashes of the first stars, the pattern of elements that made and that were incorporated in subsequent generations of stars. Observes now have found some very old stars in the halo of our galaxy, one of its oldest constituents, that likely have formed very early in the universe. These stars have only miniscule traces of heavy elements, they almost exclusively consist of the matter made by the big bang. We now believe that many of those likely have been "polluted" only by a few, maybe a single star. But the ratio of heavy elements that a star makes depends a lot on how massive is was, and how it died. So looking at the ashes of these first stars, as incorporated in the old stars we have found, may tell the story of the lives of those first stars. What will we discover?

Subject: Lessons in extreme solar wind-planetary interactions at Mercury: Results from the three MESSENGER flybys in anticipation of orbital observations in 2011

Refreshments served in Room 216 Physics after colloquium

The most stringent tests of physical theories are often provided by extremes. The planet Mercury’s interaction with the solar wind provides one such case for magnetospheric physics. Mercury is unique in that it possesses no significant ionosphere, and owing to the planet’s comparatively small magnetic moment, yielding a surface field one percent of Earth’s, Mercury’s magnetosphere is small and entirely dominated by the solar wind interaction. In solar orbit from 0.31 to 0.47 AU heliocentric distance, Mercury is also exposed to solar wind densities four to ten times higher than at Earth, an interplanetary magnetic field (IMF) about three times stronger, and a predominantly radial IMF, which changes the basic nature of the bow shock structure and dynamics. Finally, length and time scales that are widely separated at Earth and other solar system magnetospheres merge in the Mercury system. Energetic (>20 keV) protons and even thermal heavy ions have gyroradii comparable to the radius of Mercury’s magnetosphere. The largest-scale fluid-mode waves have transit times through the magnetosphere comparable to ion gyro-frequencies. Thus the convenient scale ordering that applies to other systems breaks down at Mercury. This seminar provides a summary of the initial findings from NASA’s Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. Launched in August 2004, the MESSENGER spacecraft has successfully completed six planetary gravity assist maneuvers, one at Earth, two at Venus, and three at Mercury, placing the spacecraft on target for insertion into orbit about Mercury in March 2011. Results from the three Mercury flybys reveal a rapid-fire electrodynamic system with a magnetic recirculation timescale of only tens of seconds, magnetic reconnection events at least an order of magnitude more intense than at Earth, and large-scale boundary structures unique to Mercury. The correspondence with ion-kinetic/electron-fluid simulations give tantalizing suggestions of new physical insights that will be gained once the comprehensive survey in Mercury orbit begins in 2011.

Electronic confinement at nanoscale dimensions remains a central means of science and technology. In this talk, I will describe a method for producing extreme nanoscale electronic confinement at the interface between two normally insulating oxides, LaAlO3 and SrTiO3. Using a conducting atomic-force-microscope probe, we can create nanoscale conducting islands, nanowires, tunnel junctions and field-effect transistors, with spatial dimensions comparable to the diameter of a single-wall carbon nanotube (~2 nm). These structures are created in ambient conditions at room temperature, and can be erased and rewritten repeatedly. This new, on-demand nanoelectronics platform has the potential for widespread scientific and technological exploitation.